In general, exhaust gases discharged through the operation of a variety of combustion reactors in various types of facilities, such as power plants, ironworks, and incinerators, may be incompletely combusted due to low temperatures, moisture contents, insufficient amounts of oxygen, and the like. Carbon monoxide (CO), a most common gas discharged to the air through incomplete combustion, has a serious effect on the supply of oxygen to the human brain when inhaled into the human respiratory tract. Thus, strong regulations for reducing the CO concentrations of exhaust gases discharged from thermal power plants, ironworks, and means for transportation, such as vehicles, will enter into force.
Therefore, oxidation catalysis systems for converting harmful components, such as carbon monoxide and hydrocarbons, into non-harmful components have been developed. FIG. 1 illustrates a catalytic converter as an example of such oxidation catalysis systems. The catalytic converter has a structure in which the surface of a porous ceramic filter including a substrate and a carrier is coated with catalyst particles. The catalyst of the catalytic converter allows carbon monoxide or hydrocarbons introduced into the catalytic converter to react with oxygen supplied to the catalytic converter. Through this reaction, carbon monoxide or hydrocarbons are converted into carbon dioxide or water, which may then be discharged from the catalytic converter.
Here, an element such as platinum (Pt) or rhodium (Rh) having superior reactivity and stability is typically used for the catalyst coating the surface of the porous ceramic filter. However, Pt and Rh are rare earth metals having limited reserves, while the prices thereof are recently showing rapid growth due to increased demand therefor. This results in increases in the fabrication costs of exhaust gas purification filters. In addition, Pt may be disadvantageously deteriorated due to the growth or shedding of particles when exposed to exhaust gases, the temperature of which ranges from 500° C. to 600° C., over a long period of time, such that the efficiency of exhaust gas purification is lowered.